However, not as well known is the fact that such methods have serious flaws which are often glossed over, or ignored when writing on, or discussing this subject in public. that (the) half-lives (of uranium-thorium-lead) are not constant but vary with time. comes from the study of pleochroic haloes which form in a rock in the following way.Another pertinent thing that's also ignored, minimized, or scoffed at are the numerous other scientific methods of dating the earth, solar system, and or universe that yield much younger ages than 500 million years (max). When a rock crystallises, the crystals of the minerals in the rock often enclose minute grains of other minerals which contain uranium and thorium.Whereas biblical chronologies favored the shorter reaches of that range, scientific estimates favoring older ages were based on a variety of terrestrial and celestial observations.
Both the physical geologists and paleontologists could point to evidence that much more time was needed to produce what they saw in the stratigraphic and fossil records.
As one answer to his critics, Kelvin produced a completely independent estimate -- this time for the age of the Sun.
Ask a geologist when the Paleogene period started and odds are very good the answer will be about 65.5 million years ago.
Ask about the Carboniferous and you’ll likely hear 359 million years ago.
With the exception of Carbon-14, radiometric dating is used to date either igneous or metamorphic rocks that contain radioactive elements such as uranium. Now when the uranium or thorium disintegrates, the alpha particles which are emitted are slowed down by the crystals in which the grains of the uranium- or thorium-bearing minerals are embedded.
And even though various radioactive elements have been used to "date" these rocks, for the most part, the methods are basically the same. This means that if you had some pure uranium-238 with no lead in it, 4.5 billion years later one half of it would have decayed into its stable daughter product (lead-206). Where these alpha particles finally stop, crystal deformation occurs (and) shows up as a discolouration or a darkening of the crystals.In other words, the magnitude of the radius of a pleochroic halo in a particular crystal depends on the half-life of the decay responsible for the alpha particle emission. the radii of pleochroic haloes corresponding to a definite decay in a particular mineral are ...(the same) size, then it can be safely assumed that the half-life of that decay is a constant.His result was in close agreement with his estimate of the age of the earth.The solar estimate was based on the idea that the energy supply for the solar radioactive flux is gravitational contraction.was published, the earth was "scientifically" determined to be 100 million years old. In 1947, science firmly established that the earth was 3.4 billion years old.